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Mental state decoding so far has unveiled cognitive contents using functional MRI task-performance data. The challenge emerges for task-free conditions, during which mental states are ongoing, highly dynamic, and heterogeneous. With the aim to predict task-free mental state reportability, we assume that the regional dynamic coupling and decoupling of the brain’s functional activity to and from the underlying anatomy might be a comprehensive feature-set for such purpose. By means of a mathematical model based on graph signal processing, we will seek to predict ongoing mental states of the task-free periods during experience-sampling with above chance-level accuracy. A chance-level prediction would suggest that structure-function metrics might not suffice to brain read task-free data, therefore calling for more sensitive features. On the other hand, a high classification performance would suggest that we will be on route for deciphering more nuanced content of ongoing experience which can serve in evaluating noncommunicating clinical populations.

Auditory language comprehension recruits cortical regions that are both close to sensory-motor landmarks (supporting auditory and motor features) and far from these landmarks (supporting word meaning). We investigated whether the responsiveness of these regions in task-based functional MRI is related to individual differences in their physical distance to primary sensorimotor landmarks. Parcels in the auditory network, that were equally responsive across story and math tasks, showed stronger activation in individuals who had less distance between these parcels and transverse temporal sulcus, in line with the predictions of the “tethering hypothesis,” which suggests that greater proximity to input regions might increase the fidelity of sensory processing. Conversely, language and default mode parcels, which were more active for the story task, showed positive correlations between individual differences in activation and sensory-motor distance from primary sensory-motor landmarks, consistent with the view that physical separation from sensory-motor inputs supports aspects of cognition that draw on semantic memory. These results demonstrate that distance from sensorimotor regions provides an organizing principle of functional differentiation within the cortex. The relationship between activation and geodesic distance to sensory-motor landmarks is in opposite directions for cortical regions that are proximal to the heteromodal (DMN and language network) and unimodal ends of the principal gradient of intrinsic connectivity.

Spatial or temporal aspects of neural organization are known to be important indices of how cognition is organized. However, measurements and estimations are often noisy and many of the algorithms used are probabilistic, which in combination have been argued to limit studies exploring the neural basis of specific aspects of cognition. Focusing on static and dynamic functional connectivity estimations, we propose to leverage this variability to improve statistical efficiency in relating these estimations to behavior. To achieve this goal, we use a procedure based on permutation testing that provides a way of combining the results from many individual tests that refer to the same hypothesis. This is needed when testing a measure whose value is obtained from a noisy process, which can be repeated multiple times, referred to as replications. Focusing on functional connectivity, this noisy process can be: (a) computational, for example, when using an approximate inference algorithm for which different runs can produce different results or (b) observational, if we have the capacity to acquire data multiple times, and the different acquired data sets can be considered noisy examples of some underlying truth. In both cases, we are not interested in the individual replications but on the unobserved process generating each replication. In this note, we show how results can be combined instead of choosing just one of the estimated models. Using both simulations and real data, we show the benefits of this approach in practice.

Supplementary Information

Experience is not always tied to events taking place in the environment. We often generate thoughts, images and feelings unrelated to the events in the here and now. Important aspects of these self-generated experiences are stable over time within an individual but are also associated with various dispositional traits (such as ADHD or depression). In our current study, we explored whether task-free functional imaging can shed light on whether these associated dispositional features depend on common or distinct underlying mechanisms. We acquired resting state functional magnetic resonance imaging data from a large cohort of participants and sampled their experience during the scan by asking them to retrospectively report their thoughts. In a separate experimental session, participants completed a battery of measures reflecting a range of different dispositional traits. Independent component analysis identified a set of whole-brain functional networks, and we modelled how the associations between each of these nodes correlated with metrics of ongoing thought at rest as well as with dispositional indices of physical and mental health. Behaviourally, we found evidence of association between patterns of ongoing experience emphasising visual imagery and aspects of disposition that reflected high levels of self-consciousness, depression and attentional problems. We found that increased connectivity between a posterior parietal network and a lateral fronto-temporal network was associated with more reports of visual imagery at rest. Furthermore, a pattern of decoupling between the brainstem and a lateral visual network was associated with dispositional internal focus (elevated self-consciousness, rumination and attentional problems). Critically, we found that these two brain-cognition relationships were related: the correlation between parietal-frontal regions and reports of visual imagery was stronger for individuals who also had stronger connectivity between aspects of the brain stem and cerebellum with visual cortex. Together, these results suggest that unique patterns of neural organisation reflect trait variance both in ongoing patterns of thought at rest and associated dispositional traits. Furthermore, our results suggest that accounting for trait-like dispositional patterns associated with different patterns of ongoing experience is important when exploring the neural mechanisms supporting different elements of self-generated experience.

Rhythmic activity in populations of neurons is associated with cognitive and motor function. Our understanding of the neuronal mechanisms underlying these core brain functions has benefitted from demonstrations of cellular, synaptic, and network phenomena, leading to the generation of discrete rhythms at the local network level. However, discrete frequencies of rhythmic activity rarely occur alone. Despite this, little is known about why multiple rhythms are generated together or what mechanisms underlie their interaction to promote brain function. One overarching theory is that different temporal scales of rhythmic activity correspond to communication between brain regions separated by different spatial scales. To test this, we quantified the cross-frequency interactions between two dominant rhythms-theta and delta activity-manifested during magnetoencephalography recordings of subjects performing a word-pair semantic decision task. Semantic processing has been suggested to involve the formation of functional links between anatomically disparate neuronal populations over a range of spatial scales, and a distributed network was manifest in the profile of theta-delta coupling seen. Furthermore, differences in the pattern of theta-delta coupling significantly correlated with semantic outcome. Using an established experimental model of concurrent delta and theta rhythms in neocortex, we show that these outcome-dependent dynamics could be reproduced in a manner determined by the strength of cholinergic neuromodulation. Theta-delta coupling correlated with discrete neuronal activity motifs segregated by the cortical layer, neuronal intrinsic properties, and long-range axonal targets. Thus, the model suggested that local, interlaminar neocortical theta-delta coupling may serve to coordinate both cortico-cortical and cortico-subcortical computations during distributed network activity. NEW & NOTEWORTHY Here, we show, for the first time, that a network of spatially distributed brain regions can be revealed by cross-frequency coupling between delta and theta frequencies in subjects using magnetoencephalography recording during a semantic decision task. A biological model of this cross-frequency coupling suggested an interlaminar, cell-specific division of labor within the neocortex may serve to route the flow of cortico-cortical and cortico-subcortical information to promote such spatially distributed, functional networks.

When not engaged in the moment, we often spontaneously represent people, places and events that are not present in the environment. Although this capacity has been linked to the default mode network (DMN), it remains unclear how interactions between the nodes of this network give rise to particular mental experiences during spontaneous thought. One hypothesis is that the core of the DMN integrates information from medial and lateral temporal lobe memory systems, which represent different aspects of knowledge. Individual differences in the connectivity between temporal lobe regions and the default mode network core would then predict differences in the content and form of people's spontaneous thoughts. This study tested this hypothesis by examining the relationship between seed-based functional connectivity and the contents of spontaneous thought recorded in a laboratory study several days later. Variations in connectivity from both medial and lateral temporal lobe regions was associated with different patterns of spontaneous thought and these effects converged on an overlapping region in the posterior cingulate cortex. We propose that the posterior core of the DMN acts as a representational hub that integrates information represented in medial and lateral temporal lobe and this process is important in determining the content and form of spontaneous thought.